Thanks, Perque, for "citing" me as an expert () but my expertise is mostly on human insect-borne diseases and not plants! At any rate, the disease (olive quick decline syndrome) is due to the tree infection with a bacterium (Xylella fastidiosa) and there's hardly anything one can do other than... burning the trees. By now, 6 years or so after the epidemic started in Puglia, the disease has spread to France and Spain. From a purely self-centered interest, I'm happy to note that it is spreading westwards and not down to us (although it can easily come to Greece as well through the import of sick trees from infected areas (Xylella will infect several kinds of trees, not only olive). Locally, the disease spreads from tree to tree through insects, among which a few cicada species. As mentioned by Perque, there is no health danger to humans by OQDS but it does indeed represent a huge social/economic threat to the Mediterranean region.